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City of Flagstaff to Host Ribbon Cutting Ceremony for Biogas (Methane) Cogeneration Plant

October 9, 2008

The demand for renewable projects continues to rise as technologies improve and utility rates continue to increase. The biogas cogeneration plant is the third phase of a multi-phased conservation effort by the City to lead by example and encourage other community stakeholders to make similar commitments to the environment, all while saving the City $145,000 plus per year in energy costs over the next 20 years.

The City of Flagstaff and APS Energy Services yesterday hosted a ribbon-cutting and grand opening ceremony for the Wildcat Hill Waste Water Treatment Plant (WWTP) Biogas Cogeneration Plant. The plant provides the Wildcat Hill WWTP with a biogas reciprocating engine intended to be fueled in whole using digester gas (methane) available from Wildcat Hill WWTP. The result of this cogeneration process will be a maximum electric utility offset of 292 kW of electric power at a 7,000 foot elevation at full load.

Recoverable thermal output from the engine jacket and exhaust, estimated at 1.27 MBTU/Hr, offsets the natural gas used by the existing boiler to heat water used in the digester process and for building heating. This is accomplished by circulating the boiler water through a plate and frame heat exchanger which extracts heat from the generator jacket cooling circulating water and heat recovery systems.

“This project is a perfect example of how committed the City of Flagstaff is to energy conservation in our municipal operations. It is also an important part of our efforts to reduce greenhouse gas emissions from our operations by the year 2012,” said Sara Presler, City of Flagstaff Mayor. “We hope to serve as leaders to the Flagstaff community and encourage everyone to follow in our footsteps to increase energy efficiency and reduce greenhouse gas emissions.”

The project also includes a digester gas conditioning skid which removes moisture and detrimental siloxanes from the DG fueling the engine. “This will significantly reduce operations and maintenance costs and extend the life of the reciprocating engine. Additionally, the cogeneration unit has the capability of remote diagnostics and remote adjustment to the operation of the unit. This capability will improve unit availability and provide quick response to selective alarm situations, which will be the first line of defense prior to dispatching a local certified technician.

This project is the most recent in a long line of city-wide energy conservation and renewable energy projects in which APS Energy Services and the City of Flagstaff have partnered. Projects include a sophisticated energy management system, allowing for remote centralized control of multiple city buildings; revitalization of the Jay Lively Ice Arena encompassing energy and ice system infrastructure improvements and building repair; completion of city-wide street lighting and walk sign retrofit to the latest in efficient LED lighting technology; and a 15kW solar installation at City Hall. Conservation efforts have resulted in a cumulative annual emission reduction of approximately 7 million pounds of carbon dioxide (CO2) to the City of Flagstaff.

According to Rick Becker, APS Energy Services’ Senior Account Manager, “the cost of this project was $1.7 million; however, through utility rebates made available by Arizona Public Service, this cost will be offset by approximately $100,000 per year over the next 10 years.”

The City’s Wildcat Hill Plant is a six-million gallon-per-day advanced wastewater treatment facility. The process uses screening, primary sedimentation, bio-filtration, secondary sedimentation, disinfection and filtration. Effluent from the plant is used for irrigation in east Flagstaff or discharged into the Rio de Flag. The facility also treats the sludge generated from the Rio de Flag Wastewater Plant in west Flagstaff as well as its own.

The City of Flagstaff is committed to meeting its existing needs without compromising the ability of future generations to meet their own needs. The long-term impacts of policy choices will be considered to ensure a sustainable legacy.

APS Energy Services

Headquartered in Tempe, AZ, APS Energy Services is a full-services energy company and has completed energy efficiency and renewable projects throughout the Southwest. For more information about APS Energy Services, please visit their webpage at www.apses.com.




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